Grouping array of objects base on multiple property value of each object-CodePudding

I have an array of object of students from different schools and country. I want them to be grouped by name of school and country. How can I do the nested key value. I am new in programming and this one is hard for me. Can someone teach me on how to do this. thank youu.

Example:


//array of students
$students = [
  [
    “country” => “japan”,
    “school”  => “kyoto university”,
    “name”    => “Naruto Uzumaki”
  ],
  [
    “country” => “usa”,
    “school”  => “harvard university”,
    “name”    => “Naruto Uzumaki”
  ], 
  [
    “country” => “japan”,
    “school”  => “tokyo university”,
    “name”    => “sasuke Uchiha”
  ],
  [
    “country” => “japan”,
    “school”  => “tokyo university”,
    “name”    => “kakashi hatake”
  ],
];

Results:

[
  “japan” => [
      “kyoto university” => [
          [
            “country” => “japan”,
            “school”  => “kyoto university”,
            “name”    => “Naruto Uzumaki”
          ],
      ],

      “tokyo university” => [
          [
            “country” => “japan”,
            “school”  => “tokyo university”,
            “name”    => “sasuke Uchiha”
          ],
          [
            “country” => “japan”,
            “school”  => “tokyo university”,
            “name”    => “kakashi hatake”
          ],
      ],

   ],
   

   “usa” => [
       “harvard university” => [
           [
             “country” => “usa”,
             “school”  => “harvard university”,
             “name”    => “Naruto Uzumaki”
           ],
       ]
     ]

]

How can I grouped the students by country and school like you see in my “results”.

CodePudding user response：

Pretty much creating an object or using an existing one. First create country object if not exists, then create school object under it (if not exists) then push to it.

$result = [];
foreach ($students as $student) {
    $country = $student['country'];
    $school = $student['school'];
    $result[$country] = isset($result[$country]) ? $result[$country] : [];
    $result[$country][$school] = isset($result[$country][$school]) ? $result[$country][$school] : [];
    $result[$country][$school][] = $student;
}
print_r($result);

Output:

Array
(
    [japan] => Array
        (
            [kyoto university] => Array
                (
                    [0] => Array
                        (
                            [country] => japan
                            [school] => kyoto university
                            [name] => Naruto Uzumaki
                        )

                )

            [tokyo university] => Array
                (
                    [0] => Array
                        (
                            [country] => japan
                            [school] => tokyo university
                            [name] => sasuke Uchiha
                        )

                    [1] => Array
                        (
                            [country] => japan
                            [school] => tokyo university
                            [name] => kakashi hatake
                        )

                )

        )

    [usa] => Array
        (
            [harvard university] => Array
                (
                    [0] => Array
                        (
                            [country] => usa
                            [school] => harvard university
                            [name] => Naruto Uzumaki
                        )

                )

        )

)

CodePudding user response：

Loop over each row
Create convenient variables from the row's associative elements with extract()
Push the row into the nested associative structure using two of the three generated variables

Code: (Demo)

$result = [];
foreach ($students as $student) {
    extract($student);
    $result[$country][$school] = $student;
}
var_export($result);

It is not at all necessary to instantiate/declare parent elements before push child elements when using square brace pushing syntax. If you are using array_push(), the parent element must be declared in advance.